Load management thermostat

ABSTRACT

A thermostat is provided that is capable of reliably reducing the operation of an air conditioner and other systems to provide energy cost savings to the consumer and load reduction to a utility provider. The thermostat includes at least one sensor configured to communicate information indicative of the temperature within the space, and a memory for storing at least one temperature offset value associated with a request for reduced heating or reduced cooling operation. The thermostat further includes a controller in communication with the at least one sensor, which is configured to periodically determine a temperature value for the space and to control heating or cooling of the space until the determined temperature value has substantially reached the set-point temperature. The periodically determined temperature value is in part based on information received from the at least one sensor, and may include at least one temperature offset value when a request for reduced operation has been received by the thermostat.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/801,855 filed on May 11, 2007, now U.S. Pat. No. 7,775,454 to beissued Aug. 17, 2010, which claims priority to U.S. patent applicationSer. No. 11/156,973, filed Jun. 20, 2005, entitled “Thermostat HavingDefault Curtailment Temperature Settings”. The entire disclosures ofeach of the above applications are incorporated herein by reference.

FIELD

The present disclosure relates thermostats for controlling the level ofoperation of one or more systems to correspond with a time-of-use energyrate, and to thermostats that can provide demand side management controlto an electric utility provider.

BACKGROUND

As the demand for electrical power increases during the day, the utilityprovider experiences an increase in the cost of generating electricalpower as a result of secondary “peak” power plants that are switched onto supplement off-peak power generating plants. In situations where thepeak demand begins to exceed the power generating capacity of theutility's off-peak and peak power plants, the utility may engage indemand side management, which curtails or reduces consumer energy usageto keep the demand from exceeding capacity. Utilities engaging in demandside management transmit a signal to various users of electrical energyto reduce the amount of energy they use during peak demand periods byturning off electrical loads such as air conditioners. In the example ofan air conditioner controlled by a conventional thermostat, the utilityprovider may request reduced air conditioner operation by changing theset point temperature of the thermostat. Previous attempts have beenmade to provide a load-shedding thermostat that can offset thetemperature set point to reduce the amount of energy used during peakdemand periods. This would allow the utility to be able to lower energyconsumption to keep the peak demand from exceeding their capacity, andthe user would be able to save on their energy bill. However, thismethod of offsetting the temperature setting of a thermostat by apredetermined amount cannot always be relied upon to reduce theoperating level of the air conditioner, since the user may respond tothe displayed change in set point temperature by over-riding the utilitychange to the set-point temperature setting.

SUMMARY

The present disclosure relates to thermostats that provide loadreduction features to reduce energy demand during peak energyconsumption periods. Various embodiments of a thermostat are providedthat are capable of reliably reducing the operation of an airconditioner and other systems to provide energy cost savings to theconsumer and also load reduction to a utility provider. The variousthermostat embodiments include at least one sensor configured tocommunicate information indicative of the temperature within the space,and a memory for storing at least one temperature offset valueassociated with a request for reduced heating or reduced coolingoperation. The various thermostat embodiments further include acontroller in communication with the at least one sensor, which isconfigured to periodically determine a temperature value for the spaceand to control heating or cooling of the space until the determinedtemperature value has substantially reached the set-point temperature.The periodically determined temperature value is in part based oninformation received from the at least one sensor, and may include atleast one temperature offset value when a request for reduced operationhas been received by the thermostat.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 shows a space temperature over a given time period in which oneembodiment of a thermostat and method control air conditioner operationusing an offset, in response to a first request for reduced operation;

FIG. 2. shows a space temperature over a given time period in which airconditioner operation is controlled using a second offset, in responseto a second request for reduced operation;

FIG. 3 shows a flow chart for a second embodiment of a thermostat andmethod according to the principles of the present disclosure;

FIG. 4 shows an illustration of a temperature profile provided byanother embodiment of a thermostat and method according to theprinciples of the present invention;

FIG. 5 shows a graph illustrating the reduced operation of an airconditioner system using a determined temperature value including anoffset;

FIG. 6 shows an embodiment of a thermostat provided with a displaydevice configured to display an icon indicating that the thermostat hasbeen selectively set to the reduced mode of operation; and

FIG. 7 shows an embodiment of a thermostat provided with a displaydevice configured to display an icon indicating that the thermostat isin a reduced mode of operation.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

According to various aspects of the present disclosure, there areprovided various exemplary embodiments of thermostat that includes afeature enabling a request for reduce cooling or heating operation. Inthe various embodiments, a thermostat is provided that is configured tohold or maintain a select set-point temperature setting. The variousdisclosed thermostat embodiments are at least configurable to operate ina “Hold” temperature mode, which controls cooling or heating to thespace to hold or maintain the user's selected set-point temperature. Insome embodiments, the thermostat may be configured to provide at leasttwo or more programmed set-point temperature settings that correspond tospecific time periods of operation, such as day or night time periods.In the “Hold” mode, the thermostat controls the operation of a heatingor cooling system to continuously condition the space, to hold the spacetemperature at the user's select set-point temperature. If the spacedoes not feel comfortable to the user, the various thermostatembodiments allow a user to temporarily adjust the “Hold” temperaturesetting by pressing the temperature up or down buttons, to request ahigher or lower setting for a short time period. For example, the usermay press the down arrow to lower the “Hold” temperature set-point of 72degrees to 70 degrees Fahrenheit, in response to which a standardsub-routine within the thermostat's software program would controlcooling to maintain the space at 70 degrees for a temporary two-hourtime period, after which the thermostat would return to normal “Hold”mode to maintain the 72 degree set-point temperature.

The various embodiments of a thermostat further comprise at least onetemperature responsive device that at least periodically outputs avariable or value that is indicative of the temperature in the space.The sensor may be any of a number of sensor types, and may comprise acrystal, oscillator or other electronic component having a frequencythat responsively changes with temperature. Alternatively, the sensormay comprise a thermistor having a resistance value that changes inresponse to changes in temperature. The sensor could also be a devicecapable of communicating a voltage value that correlates to, or isindicative of, the temperature sensed in the space. The sensor mayinclude circuitry to permit the sensor the communicate an absolute valueof the temperature to a tenth of degree Fahrenheit. Likewise, the sensormay also include circuitry to enable communication of temperatureinformation on a periodic basis, or upon request, such as when promptedby a microprocessor of the thermostat. Accordingly, the at least onesensor in the various embodiments is configured to sense and communicateinformation that is indicative of the temperature in the space.

The various embodiments of a thermostat further include a controllerthat is in communication with the at least one sensor. Since the sensedtemperature varies over time, the controller is configured toperiodically determine a temperature value for the space, which isstored as the current temperature value for the space. Each time thethermostat controller determines or updates the temperature value forthe space, the controller uses information communicated from the atleast one sensor in determining the space temperature value, which isthen stored in a memory. The stored value may, for example, replace apreviously stored space temperature value, or may be stored as part of adatabase of historical temperature values over time. Since the spacetemperature value varies over time and must be repeatedly determined bythe controller, the controller may readily offset the determinedtemperature value prior to storing the space temperature value inmemory. For example, the software associated with the thermostat'scontroller may, in its determination of the space temperature value,include an offset value when a certain condition is true (such as thereceipt of a request for reduced heating or cooling operation within apredetermined time period). Such a software provision enables thechanging of the space temperature value to effect a reduction inoperation, without requiring software complexity or subroutines that arerequired to allow a utility provider to change the set-point temperatureto reduce operation.

It should be noted that offsetting the space temperature is not the sameas changing the thermostat's set-point temperature setting. If thethermostat's controller were configured to permit a Utility provider totemporarily change the thermostat's cooling set-point temperature, thethermostat would likely require a “load-shed” subroutine to deviate fromnormal operation and control cooling operation to the utility's changedset-point temperature for a temporary duration. The controller may alsoneed to be configured to allow the user to override the utilityprovider's set-point and subsequently change the set-point temperatureagain, which would likely require another sub-routine for deviating fromthe previous “load-shed” subroutine. Changing the set-point temperaturewould therefore lead to greater software and controller costs. For costreasons, thermostats are designed to use programs of minimal size, withsimple microprocessors having a limited memory. A software configurationthat permits a utility provider to change the set-point temperaturewould require a sub-routine for deviating from normal operation, toenable interim control for a temporary time period using the Utilityprovider's changed set-point temperature (which change would also bedisplayed on the thermostat's display). This type of additionalsubroutine can add to the complexity and size of the software program,and may necessitate a more costly and sophisticated microprocessor toaccommodate the size of the software, thereby increasing thethermostat's cost.

Moreover, permitting a utility provider to change the set-pointtemperature would be less effective in reducing operation to shed energydemand, since the user would readily see the Utility's change to theset-point temperature on the display of the thermostat, and would bemore tempted to over-ride the Utility's changed set-point. Thus, aset-point temperature change scheme accordingly requires the inclusionof subroutines that add to the software's complexity and thecontroller's memory requirements for the thermostat, and still would notadequately assure curbing of energy consumption through reduced heatingor cooling operation.

The various embodiments of a thermostat do not alter the set-pointtemperature of the thermostat upon receiving a request for reducedheating or cooling operation. Rather, the various embodiments provide athermostat that displays a current temperature value for the space(eg.—73° F., for example), and the set-point temperature (eg.—72° F.,for example). In the above temperature situation, the thermostat wouldestablish cooling operation to reduce the 73° F. temperature. Where aUtility provider's request for reduced cooling operation is received bythe thermostat, the controller subsequently determines a spacetemperature value that includes, or is reduced by the at least oneoffset (eg.—to 70° F., for example), which artificially reduces thespace temperature value relative to the unchanged set-point temperature.It should be noted that the temperature offset value is preferablywithin the range of 1 to 8 degrees Fahrenheit. Such an offset to thespace temperature would thereby satisfy the set-point temperature andend cooling operation to thereby reduce the demand for energy. Thus, thedisplayed set-point temperature selected by the user remains unchanged,while the displayed space temperature is transparently lowered. As such,the user would perceive the space to be cooled to the user's selectedset-point temperature. Such a configuration simplifies the use ofload-shedding thermostat for the user, since the user would only see thedisplay of the user's selected set-point temperature and the display ofthe determined temperature value for the space. Since this type ofrequest for reduced operation would be transparent to the user (as theuser's set-point temperature setting would remain unchanged), the userwould be less likely to opt out, or over-ride the utility's request forreduced cooling operation. Accordingly, the various embodiments comprisea controller configured to periodically determine a space temperaturevalue that can include at least one offset, to allow for effectivelyreducing heating or cooling operation where a request for reducedoperation has been received (by a utility provider for example). Therequest for reduced operation is preferably a signal transmitted by autility provider that is received by the thermostat, either wirelesstransmission means or through power-line transmission means. It shouldbe noted that the request for reduced operation may also be an energysavings mode that the user may change from a normally disabled defaultsetting to an enabled setting, such that the thermostat initiatesreduced operation during “peak” energy demand periods at the user'srequest. Such thermostat embodiments do not require any softwaresubroutines for deviating from normal operation. The followingdescription of one embodiment is given as an example to illustrate thisadvantageous feature.

In one embodiment, a load-shedding thermostat is provided forcontrolling the operation of at least a cooling system for conditioninga space. The thermostat comprises at least one sensor that is configuredto communicate information indicative of the temperature within thespace. In the first embodiment, the sensor produces a signal thatincreases in frequency with an increase in temperature, or a signal thatincreases in resistance with an increase in temperature. The sensorsignal communicates information, or a value, that is indicative of thesensed temperature in the space, which value is received by a controllerof the thermostat and converted to a temperature value.

The first embodiment of a thermostat further comprises a memory forstoring at least one temperature offset value associated with at leastone request for reduced cooling operation. The at least one offset valuemay be a value that incrementally changes with operating time, or may bea predetermined value associated with a particular degree ofcurtailment. Where a request has been received for reduced cooling (asopposed to reduced heating), the at least one temperature offset in thefirst embodiment comprises a offset value of −3 degrees Fahrenheit. Theat least one temperature offset may further include a second offset of−3 degrees Fahrenheit, which may be associated with a tiered energyusage rate or a second request for additional reduced cooling operation,for example. Thus, the temperature offset value may comprise a pluralityof incremental offset values that incrementally offset the spacetemperature to provide for reduced cooling in response to successiverequests for reduced operation. The offset values are stored in a memorythat is preferably a non-volatile electronically erasable programmableread-only memory (EEPROM). This memory may be a stand-alone memorycomponent, but is preferably included in a microprocessor controller ofthe thermostat.

The first embodiment of a thermostat further includes a controller incommunication with the at least one sensor, which controller ispreferably a microprocessor that includes a software program forcontrolling the operation of at least a cooling system. Themicroprocessor controller is configured to periodically determine atemperature value for the space and to control cooling of the spaceuntil the determined space temperature value has substantially reachedthe set-point temperature. It should be noted that the controller maydiscontinue cooling operation when the space temperature value is withina fraction of a degree above or below the set-point temperature, ratherthan the exact moment that the set-point temperature is reached.

The microprocessor controller determines the temperature value for thespace based on information received from the at least one sensor, andmay include at least one temperature offset value in determining thespace temperature value where a request for reduced operation has beenreceived within a predetermined time period. The software associatedwith the thermostat's controller is configured to, in its determinationof the space temperature value, include an offset value when a certaincondition is true, such as where a request for reduced cooling operationhas been received by the thermostat within a predetermined time period.It should be noted however, that similar programming means employed insoftware may also be used, which are suitable for providing aconditional offset to a determined value. The thermostat furthercomprises a display device that displays to the user the set-pointtemperature, and the determined temperature value for the space, withoutany indication of whether the temperature value for the space includes atemperature offset value.

Where a request for reduced operation has been received within apredetermined time period, the controller includes at least onetemperature offset value in determining the space temperature value. Thepredetermined time period may comprise a three hour period, for example,which would allow a utility provider to communicate a signal to requestreduced cooling operation that would remain in effect for three hours.During this predetermined time period, the thermostat's microprocessorcontroller would continue to offset the determined temperature value forthe space. The offset would artificially lower the space temperaturevalue, such that the set-point temperature is either satisfied or morequickly reached, to thereby reduce the need for cooling operation.

For example, in the situation of a thermostat with a user-selectedset-point temperature of 72 degrees Fahrenheit, in a space that is at 73degrees Fahrenheit, the thermostat would control the operation of thecooling system to lower the space temperature to 72 degrees. Uponreceiving a request for reduced operation (from either a Utilityprovider or the user of the thermostat), the thermostat's controllerwould offset the space temperature value by −3 degrees, to 70 degreesFahrenheit. Since the 70 degree space temperature value is below the 72degree set-point temperature value, the thermostat controller woulddiscontinue cooling operation. The cooling system would remain off for asubstantial time period, until the 70 degree space temperature valueslowly rises above the 70 degree set-point temperature. This would havethe effect of reducing the operation of the cooling system, to therebyreduce energy demand on the utility provider.

During the predetermined time period, the controller may be configured(by a Utility provider, for example) to discontinue cooling operationfor at least a minimum off-time period after the space temperature valuehas substantially reached the set-point temperature, to thereby providea minimum off time that will further reduce operation of the coolingsystem after the initial offset. After the predetermined time period hastranspired, the controller is configured to subsequently determine aspace temperature value that is absent any temperature offset value,since the request for reduced operation received by the thermostat is nolonger within the predetermined time period. Thus, the request forreduced operation is discontinued after the predetermined timed periodfollowing the receipt of the request has transpired. At such point, thethermostat returns to normal operation of maintaining the 72 degree setpoint temperature.

In the first embodiment of a thermostat, the displayed 72 degreeset-point temperature selected by the user remains unchanged, while thedisplayed space temperature is transparently lowered to 70 degrees. Assuch, the user would perceive the space to be cooled to the user's 72degree set-point temperature. Since this type of request for reducedoperation would be transparent to the user, the user would be lesslikely to over-ride the utility's request for reduced cooling operation,through adjustment of the temperature. Accordingly, the first embodimentof a thermostat provides for effectively reducing cooling operationwhere a request for reduced operation has been received from a Utilityprovider, or alternatively a user of the thermostat. However, should anoccupant of the space feel uncomfortable, the occupant may temporarilyadjust the “Hold” set-point temperature setting by pressing thetemperature up or down buttons, to request a higher or lower setting fora short time period. For example, an occupant or user may press the downarrow to lower the “Hold” temperature set-point of 72 degrees to 70degrees Fahrenheit, in response to which a standard sub-routine withinthe thermostat's software program would control cooling to maintain thespace at 70 degrees for a temporary two-hour time period. No additionalsoftware subroutines would therefore be required to over-ride theutility's request for “load-shed” or reduced operation. As such, athermostat is provided with load-shedding and over-ride capability thatdoes not require software complexity or more costly sophisticatedmicroprocessor control.

For purposes of illustration only, the operation of an air conditionermay be controlled by a thermostat and method according to the firstembodiment as described in the following exemplary scenario. Referringto FIG. 1, a chart is provided illustrating the temperature of a spaceover a given time period, during which the thermostat successivelyinitiates operation of the air conditioner. For illustrative purposes,the scenario assumes a conditioned space that experiences an increase of2 degrees Fahrenheit per hour during the daytime when outside ambienttemperatures reach their peak.

Referring to FIG. 1 at 100, the thermostat determines that thecalculated temperature value for the space is at least 0.5 degreesFahrenheit above a 74 degree set-point temperature, and initiatesoperation of the air conditioner. The air conditioner runs forapproximately 20 minutes, after which the thermostat's determinedtemperature value for the space is 74 degrees, and the air conditioneris shut off at 110. During the next 15 minutes, the temperature in thespace gradually increases at a rate of 2 degrees Fahrenheit per hour,and reaches 74.5 degrees Fahrenheit at 120. The thermostat responsivelyinitiates operation of the air conditioner in a cyclic manner, up topoint 130. At 130, the thermostat then receives a request for reducedoperation, from an occupant or a Utility provider for example. Thethermostat then calculates a determined temperature value for the space,which is determined based on information received from the at least onesensor, and at least one temperature offset value associated with arequest for reduced operation. In this illustrative example, thetemperature offset is −3 degrees Fahrenheit. The determined temperaturevalue for the space is then 74 less 3 degrees, or 71 degrees.Accordingly, the thermostat would compare the determined temperaturevalue for the space of 71 degrees Fahrenheit relative to the 74 degreeset point temperature. The thermostat would accordingly maintain the airconditioner in an off state as the actual temperature graduallyincreases to an actual temperature of 77.5 degrees Fahrenheit, or adetermined temperature value of 77.4 degrees, after which the thermostatwould again initiate operation of the air conditioner in a cyclicmanner. This would result in a total “off” time of an hour andforty-five minutes in which energy would be saved during a peaktemperature or energy demand period. It should be noted that in thevarious disclosed embodiments, the thermostat may alternatively beconfigured to determine temperature values in degrees Celsius, and mayinclude offset values that are also in degrees Celsius.

In another illustration, a second request for curtailment of airconditioning operation is further described in the following exemplaryscenario shown in FIG. 2, which shows a chart illustrating thetemperature of a space over a given time period. The conditioned spacesimilarly experiences an increase of 2 degrees Fahrenheit per hour asabove, and has received a previous request for reduced operation thatled to a −3 degree temperature offset.

Referring to FIG. 2 at 150, the thermostat continues operation leavingoff after the end of the above scenario. The thermostat calculates adetermined temperature value for the space as 77.5 degrees Fahrenheit,less a 3 degree offset, to reach 74.5 degrees Fahrenheit. Thisdetermined temperature for the space is at least 0.5 degrees Fahrenheitabove the 74 degree set-point temperature, such that the thermostatinitiates operation of the air conditioner. The air conditioner runs forapproximately 20 minutes, after which the thermostat's determinedtemperature value for the space is 74 degrees, and the air conditioneris shut off at 160. During the next 15 minutes, the temperature in thespace gradually increases at a rate of 2 degrees Fahrenheit per hour,and reaches an actual temperature of 77.5 degrees Fahrenheit, or adetermined temperature for the space of 77.4 degrees Fahrenheit. At 170,the thermostat responsively initiates operation of the air conditionerin a cyclic manner, up to point 180. At 180, the thermostat thenreceives a subsequent request for further reduction in operation, suchas during a critical peak demand period. The thermostat then calculatesa determined temperature value for the space, which is determined basedon information received from the at least one sensor, and a temperatureoffset value associated with a second request for reduced operation. Inthis illustrative example, the temperature offset is −5 degreesFahrenheit. The determined temperature value for the space is then 77less 5 degrees, or 72 degrees. Accordingly, the thermostat would comparethe determined temperature value for the space of 72 degrees Fahrenheitrelative to the 74 degree set point temperature. The thermostat wouldaccordingly maintain the air conditioner in an off state as the actualtemperature gradually increases to 79.5 degrees Fahrenheit, after whichthe thermostat would again initiate operation of the air conditioner ina cyclic manner. This would result in an additional “off” time of anhour and fifteen minutes beyond the first hour and forty-five minuteperiod, in which period energy would be saved during a peak temperatureor energy-demand period of the day.

The above incremental offsets to the space temperature both artificiallyallow the thermostat to satisfy the set-point temperature and endcooling operation to thereby reduce the demand for energy. The displayedset-point temperature of 74 degrees remains unchanged, while thedisplayed space temperature is transparently lowered. As such, the userwould perceive the space to be cooled to the desired set-pointtemperature, and the request for reduced operation would be transparentto the user (as the user's set-point temperature setting would remainunchanged). Accordingly, the user would be less likely to over-ride arequest for reduced cooling operation, and would still have asufficiently cool temperature for the space relative to peak outsideambient temperatures.

In another aspect of the present disclosure, a method is provided forcontrolling the operation of a thermostat that is capable of receiving arequest for reduced operation of a heating or cooling system for aspace, such as during a period of peak energy demand. In one embodiment,the method comprises storing in a memory at least one temperature offsetvalue associated with a request for reduced cooling operation. Themethod further comprises the steps of receiving the communication ofinformation indicative of the temperature within a space from at leastone sensor, and periodically determining a temperature value for thespace. The periodic determination of a temperature value is determinedbased on information received from the at least one sensor, and at leastone temperature offset value when a request for reduced operation hasbeen received within a predetermined time period. The method thencontrols operation of the heating or cooling system for the space untilthe determined temperature value has substantially reached the set-pointtemperature. The method preferably includes the at least one temperatureoffset value in the determination of a temperature value for the spacefor a predetermined time period after a request for reduced heating orcooling operation has been received.

It should be noted that other embodiments of a system and method may beemployed that comprise a number of offset values, where the offset valuevaries or is incrementally changed with operating time, for example.Referring to FIG. 3, an example of a second embodiment of an energysaving method for controlling a thermostat is illustrated. In thismethod, the offset value is incremented based on the operating time ofthe air conditioner.

Not shown in FIG. 3 are the initial steps of the second methodembodiment, of storing in a memory at least one temperature offsetdefault value associated with a request for reduced cooling operation.The method also periodically receives the communication of informationindicative of the sensed temperature within a space from at least onesensor. The method also determines a temperature value for the space,based on information received from the at least one sensor and at leastone temperature offset value when a request for reduced operation hasbeen received within a predetermined time period.

Referring to FIG. 3 at step 200, the second embodiment of a method forcontrolling a thermostat determines whether the system is in a cool modein which the air conditioning system is to be operated to control thetemperature of a space. The method then determines at step 204 whetherit is in a normal mode of operation to control a space temperature, orwhether it is in an energy savings mode of reduced operation (eg.—CoolSavings mode). If the thermostat is in the reduced operation mode, thethermostat proceeds to step 208 to compare the determined temperaturevalue for the space is above the determined set point temperature, todetermine if there is a call for cooling operation. If there is a callor need for cooling, operation of the air conditioner is initiated. Themethod of this embodiment uses a compressor run-time counter fortracking the amount of time the compressor runs, and determines at step212 whether the compressor has run beyond a predetermined time, such as20 minutes, for example. For a given number of minutes beyond the twentyminute operating time, the software increments a count value at step 220(up to a user specified maximum set at step 216), which count value maybe used in determining an offset value in the calculation of adetermined temperature for the space. The offset value may beincremented by a predetermined temperature value corresponding to anincremental time period of operation beyond a minimum threshold timeperiod of operation. For example, the offset may be incremented at least1/16 of a degree Fahrenheit for each two-minute time increment ofoperation beyond a minimum threshold period of at least 15 minutes ofoperation. The offset value may initially be a default value of 0degrees, and may be incremented 1/16 of a degree for every two minutesthat the compressor runs beyond twenty minutes in a given cooling cycle.Thus, if the compressor runs for a total of 24 minutes before theset-point temperature is reached, the offset would be 2 degrees plus2/16 of a degree, or 2⅛ degree Fahrenheit. Thus, the longer thecompressor runs during cooling operation cycles, the greater will be theoffset that is subtracted from the sensed temperature in calculating adetermined temperature value for the space. Thus, the determinedtemperature for the space will be decremented over longer compressor runtimes, such that the set point temperature is reached sooner andcompressor operation is shortened. During midday when daytimetemperatures reach their peak, the air conditioner is less effective andruns longer to cool the space. It is during such periods that longer runtimes of the air conditioning compressor will occur. The present methodcurtails operation of the air conditioner during such periods byoffsetting the temperature value for the space to help reach the setpoint temperature sooner and reduce air conditioning operation. Thismethod accordingly helps to reduce cooling operation during peak energydemand periods.

Referring to FIG. 4, an illustration of a temperature profile that maybe provided by the above method is shown. A thermostat utilizing theabove method is set to a cool mode for conditioning a space, which isinitially at 77 degrees Fahrenheit as shown at 200. In thisillustration, the outdoor ambient temperature is assumed to be high,such that the space experiences a 2 degree increase per hour, or a 0.5degree Fahrenheit increase to 74.5 degrees in 15 minutes. At 208, thecontrol method for the thermostat determines if there is a call forcooling operation, by checking temperature sensor information andcalculating a determined temperature value for the space of 77.5degrees. Since the 77.5 degree determined temperature value is at least0.5 degrees above a 77 degree set-point temperature, the thermostatestablishes operation of the air conditioner. Because of the highoutside ambient conditions, the air conditioner runs for as much as 30minutes before the space is cooled to a level where the determinedtemperature value for the space is at the 77 degree set pointtemperature, and operation of the air conditioner is discontinued orshut-off. Since the air conditioner was operated for more than 20minutes, the method increments a count value during operation after 20minutes, which value may be used to determine an offset value. Forexample, the offset value may initially be a default of 0 degrees, andmay be incremented 1/16 of a degree for every two minutes that thecompressor runs beyond twenty minutes in a given cooling cycle. Thus,the 10 minutes of operation beyond the 20 minute period would result inan offset of 5/16 of a degree Fahrenheit. At the conclusion of thecooling cycle, the thermostat may calculate a determined temperaturevalue of the space that includes this 5/16 offset, to arrive at a newdetermined temperature value of 76 11/16 degrees Fahrenheit at 220.

From point 220, the determined temperature value of the space wouldagain rise in the next 15 minutes by 0.5 degrees, from 76 11/16 degreesto 77 3/16 degrees. After 15 minutes, the determined temperature has notreached the 77.5 degree trigger point, because of the offset value.Thus, the air conditioner will remain off for another 9 minutes beforethe determined temperature value increases from 77 3/16 degrees to the77½ degree trigger point at 240. Thus, the offset causes the airconditioner off time to increase from 15 minutes to 24 minutes. Once thedetermined temperature value reaches 77.5 degrees, the thermostat willagain establish operation of the air conditioner, which will again runfor 30 minutes to cool the space until the determined temperature valueis lowered to 77 degrees. The method would again increment the offsetvalue 1/16 of a degree for every two minutes of operation beyond twentyminutes in the cooling cycle, to result in a total offset value of 10/16of a degree Fahrenheit. This method of offsetting the sensed temperaturefor the space is repeated over five 30-minute cooling cycles, afterwhich a predetermined maximum temperature offset is reached, which inthis embodiment is 1½ degrees. In the 280 minute time period in whichthe air conditioner was operated for five 30-minute cycles, the airconditioner remained off after each cycle for a period of 24 minutesinstead of only 15 minutes. This resulted in 45 minutes of additionaloff time, in exchange for an increase of only 1.5 degrees in the actualsensed temperature for the space.

Referring to FIG. 5, the above method for controlling operation based ona determined temperature value including an offset provided five30-minute cycles in a time period that would normally have six 30-minutecycles based on a determined temperature absent any offset. Thus, inmid-day peak-energy demand situations when elevated outside ambienttemperatures cause air conditioners to run for longer cycle periods, theabove method results in a reduction in operation of 17 percent. In sucha method, the request for reduced operation may implemented simply by autility-provider signal to enter the thermostat into the incrementaloffset mode of operation, or by the user setting the thermostat to theincremental mode of operation. Thus, a user may be able to initiate therequest for reduced mode of operation, independent of any signal from autility provider. Moreover, the thermostat provides for such reducedoperation only during day time periods in which elevated temperaturescause the air conditioner to run longer cycles, and thereforeselectively reduces operation based on outside ambient temperatures thataffect peak energy demand periods, without requiring the use of anyoutside ambient temperature sensor.

In another aspect of the present disclosure, the thermostat is furtherprovided with a display device 300 as shown in FIG. 6, which isconfigured to display an icon 310 indicating that the thermostat is inthe reduced mode of operation. For example, the display may show thewords “Cool Savings” to indicate that the reduced operation mode hasbeen selected or enabled. Referring to FIG. 7, the thermostat displaydevice 300 has been further configured to display an Icon 320 toindicate when the thermostat has received a request for reducedoperation. For example, the display device may show the word “Save” toindicate that the thermostat is controlling operation using thedetermined temperature value for the space to reduce air conditioneroperation. In this manner, the reduced mode of operation is transparent,since the displayed set point temperature setting and displayed“determined temperature value” still appear the same. The “Save” iconprovides an inconspicuous indication that air conditioning operation hasbeen curtailed, in a manner that will not alert all occupants of thespace to avoid the temptation by such occupants to override thetemperature setting.

The advantages of the above described embodiments and improvementsshould be readily apparent to one skilled in the art, as to enablingload-shedding capability to a thermostat. Additional designconsiderations may be incorporated without departing from the spirit andscope of the invention. The description in this disclosure is merelyexemplary in nature and, thus, variations are not to be regarded as adeparture from the spirit and scope of the disclosure. Accordingly, itis not intended that the invention be limited by the particularembodiments or forms described above, but by the appended claims.

1. A thermostat for controlling a heating and/or cooling appliance for aspace to maintain a set-point temperature, the thermostat comprising: atleast one sensor configured to communicate information indicative of thetemperature within the space; a memory for storing at least one sensedtemperature offset value associated with a request for reduced operationassociated with an energy savings mode enabled by a user of thethermostat; and a controller in communication with the memory and the atleast one sensor, being configured to set an energy savings mode to anenabled setting in response to receiving a request for reduced operationfrom a user of the thermostat, the controller being configured toperiodically receive a sensed temperature value from the at least onesensor, where the controller offsets the sensed temperature value by theat least one sensed temperature offset value associated with the energysavings mode when a request for reduced operation from a user has beenreceived, to thereby determine an artificial temperature value for thespace, the controller being configured to discontinue cooling operationfor the space where the determined artificial temperature value is belowthe set-point temperature, and configured to discontinue heatingoperation for the space where the determined artificial temperaturevalue is above the set-point temperature; and a display device incommunication with the controller that displays the determinedartificial temperature value for the space instead of the actual sensedtemperature of the space, and also displays the user selected set pointtemperature without alteration, such that the alteration of the sensedtemperature for the space is transparent to the user and the user wouldbe less likely to change the setpoint temperature.
 2. The thermostat ofclaim 1 where upon receiving a request for reduced cooling operation,the controller is configured to include at least one temperature offsetvalue in the determination of the artificial temperature value for thespace for a predetermined time period after receiving the request forreduced cooling operation.
 3. The thermostat of claim 2 where thecontroller is configured to periodically determine an artificialtemperature value for the space absent any temperature offset valuewhere the controller has not received a request for reduced operationfrom a user of the thermostat within a predetermined time period.
 4. Thethermostat of claim 1 further comprising a display device that displaysto the user the set-point temperature and the periodically determinedartificial temperature value for the space, without any indication thatthe displayed artificial temperature value for the space includes atemperature offset value.
 5. The thermostat of claim 1 wherein theset-point temperature is a temperature setting selected by the user thatthe thermostat uses and controls heating or cooling operation tomaintain the temperature of the space.
 6. The thermostat of claim 1wherein the thermostat is programmable to include at least twoprogrammed set point temperature settings associated with specific timeperiods of operation.
 7. The thermostat of claim 2 wherein the offsetvalue is in the range of 1 to 8 degrees.
 8. The thermostat of claim 1wherein the at least one temperature offset value comprises a pluralityof incrementally varying offset values.
 9. The thermostat of claim 1wherein during the predetermined time period, the controller is furtherconfigured to discontinue heating or cooling operation for at least aminimum off-time period after the determined artificial temperaturevalue has substantially reached the set-point temperature.
 10. Athermostat for controlling at least a cooling system for conditioning aspace, the thermostat comprising: at least one sensor configured tocommunicate information indicative of the temperature within the space;a memory for storing at least one temperature offset value associatedwith a request for reduced heating or reduced cooling operationassociated with an energy savings mode enabled by a user of thethermostat; and a controller in communication with the memory and the atleast one sensor, being configured to set an energy savings mode to anenabled setting in response to receiving a request for reduced operationfrom a user of the thermostat, the controller being configured toperiodically receive a sensed temperature value from the at least onesensor, where the controller offsets the sensed temperature value by theat least one sensed temperature offset value associated with the energysavings mode when a request for reduced operation from a user has beenreceived, to thereby determine an artificial temperature value for thespace, the controller being configured to discontinue cooling operationfor the space where the determined artificial temperature value is belowthe set-point temperature; and a display device in communication withthe controller that displays the determined artificial temperature valuefor the space instead of the actual sensed temperature of the space, andalso displays the user selected set point temperature withoutalteration, such that the alteration of the sensed temperature for thespace is transparent to the user and the user would be less likely tochange the setpoint temperature.
 11. The thermostat of claim 10 whereupon receiving a request for reduced operation, the controller isconfigured to include at least one temperature offset value in thedetermination of the artificial temperature value for the space for apredetermined time period after receiving the request for reducedoperation from a user of the thermostat.
 12. The thermostat of claim 11where the controller is configured to periodically determine anartificial temperature value for the space absent any temperature offsetvalue where the controller has not received a request for reducedoperation from a user of the thermostat within a predetermined timeperiod.
 13. The thermostat of claim 10 further comprising a displaydevice that displays to the user the set-point temperature and theperiodically determined artificial temperature value for the space,without any indication that the periodically determined temperaturevalue for the space includes a temperature offset value.
 14. Thethermostat of claim 10 wherein the offset value is in the range of 1 to8 degrees.
 15. The thermostat of claim 10 wherein the offset isincremented by a predetermined temperature value corresponding to anincremental time period of operation beyond a minimum threshold timeperiod of operation.
 16. The thermostat of claim 15, wherein the offsetis incremented at least 1/16 of a degree Fahrenheit for each individualtime increment beyond a minimum threshold period of at least 15 minutesof operation.
 17. The thermostat of claim 10 wherein the thermostat isprogrammable to include at least two programmed set point temperaturesettings associated with specific time periods of operation.
 18. Thethermostat of claim 11 wherein during the predetermined time period, thecontroller is further configured to discontinue cooling operation for atleast a minimum off-time period after the determined artificialtemperature value has substantially reached the set-point temperature.19. A method for controlling the operation of a thermostat capable ofreceiving a request for reduced operation of a heating or cooling systemfor a space, comprising: storing in a memory at least one temperatureoffset value associated with an energy savings mode enabled by a user ofthe thermostat; setting an energy savings mode to an enabled setting inresponse to receiving a request for reduced operation from a user of thethermostat, receiving the communication of information indicative of thesensed temperature within a space from at least one sensor; andperiodically determining an artificial temperature value for the space,wherein the artificial temperature value is determined based on sensedtemperature value information received from the at least one sensor,which is offset by at least one sensed temperature offset valueassociated with the energy savings mode when a request for reducedoperation from a user has been received within a predetermined timeperiod; and controlling operation of the cooling system for the space todiscontinue cooling operation when the determined artificial temperaturevalue is below the set-point temperature; and displaying on a displaydevice the determined artificial temperature value for the space insteadof the actual sensed temperature of the space, and further displayingthe user selected set point temperature without any alteration, suchthat the alteration of the sensed temperature for the space istransparent to the user and the user would be less likely to change thesetpoint temperature.
 20. The method of claim 19 wherein, for apredetermined time period after a request for reduced operation has beenreceived, the at least one temperature offset value is added to thesensed temperature value in the determination of an artificialtemperature value for the space.